In the field of synthetic organic chemistry, protection and deprotection reactions of reactive functional groups (e.g., hydroxyl groups, amino groups, carboxyl groups, carbonyl groups, phosphodiester groups, etc.) are essential particularly for the construction of complex molecules. However, such deprotection reactions necessitate further addition of reagents, which may result in the degradation of compounds and the production of by-products.
Against this background, photolabile protecting groups that allow deprotection of reactive functional groups under neutral conditions have recently attracted attention (e.g., Non-Patent Document 1). Since photolabile protecting groups do not necessitate further addition of reagents and can be removed by light irradiation under neutral conditions, they are also applicable to acid- or base-sensitive compounds. Therefore, photolabile protecting groups have a great deal of potential as protecting groups in organic synthesis.
Moreover, since photolabile protecting groups can be eliminated by light, the size of the reaction field can be reduced to a nanoscale level. For example, in 1991, Fordor et al. successfully synthesized a DNA microarray using a photolabile protecting group by merging combinatorial chemistry with technology of photolithography for semiconductor production (Non-Patent Document 2).
Moreover, a caged compound, which is a biologically active molecule protected by a photodegradable protecting group, allowing the molecule to temporarily lose its activity, is made present in a cell, and the molecule is irradiated with light to become a bioactive substance, which can induce biological reactions. Using this technique, the time and place in which signal molecules express their functions can be controlled by the time and place in which light is irradiated; additionally, the expression level can theoretically be controlled by the amount of irradiating light. Therefore, a powerful method of real-time control of the space-time kinetics of molecules involved in signal transfer can be achieved.
Along with the development of microarrays and caged compounds described above, photolabile protecting groups that can easily be removed by light irradiation have been actively developed in recent years. Specific examples thereof are shown below. Examples of compounds currently often used in microarrays or caged compounds include nitrobenzyl derivatives represented by Formula (A) (Non-Patent Document 3) and coumarin derivatives represented by Formula (B) (Non-Patent Document 4).

These compounds almost quantitatively release alcohol upon light irradiation; however, almost no compounds that allow simple quantitative determination of deprotection are known. For example, Patent Document 1 indicates that a protecting group that has an o-aminocinnamic acid skeleton is removed from a bioactive substance by light irradiation, thereby generating a carbostyryl derivative with strong fluorescence, and that the deprotected free bioactive substance can be quantified by measuring the fluorescence intensity.
If photolabile protecting groups that facilitate the protection and deprotection of not only the hydroxyl groups and amino groups described above, but also other reactive functional groups (e.g., carboxyl groups, carbonyl groups, phosphodiester groups, etc.) are developed, such photolabile protecting groups will be very useful in the fields of organic chemistry and photochemistry, as well as biology, and have the potential of being used in a wide application.    Patent Document 1: Japanese Unexamined Patent Publication No. 1999-29500    Non-Patent Document 1: G. Mayer, A. Heckel, Angew. Chem. Int. Ed., 2006, 45, 4900    Non-Patent Document 2: Fodor, S. P. A.; Read, J. L.; Pirrung, M. C.; Stryer, L. T.; Lu, A.; Solas, D.; Science, 1991, 251, 767-773.    Non-Patent Document 3: Patchornik, A., Amit, B., and Woodward, R. B. J. Am. Chem. Soc. 1970, 92, 6333    Non-Patent Document 4: Givens, R. S. and Matuszewski, B. J. Am. Chem. Soc. 1984, 92, 6860.